1. Field of the Invention
This invention relates to a short chain linear bis(polyorganosiloxanyl)amine, its use in treating finely divided silica fillers and elastomeric compositions and cured products made therefrom.
2. Description of the Prior Art
In the silicone elastomer art, the treatment of reinforcing silica fillers is now well known as a means of retarding or preventing reaction between the surface of reinforcing filler and silicone polymer. This interaction produces what is termed "structuring" or "crepe aging" and results in a loss of workability of such mixtures. U.S. Pat. No. 3,243,404 of Martellock describes silicone compositions containing silicon-nitrogen process aids, the silicon-nitrogen material being a member selected from the class consisting of:
(A) A SILYL AMINE HAVING THE FORMULA EQU (R*).sub.b Si(N(R*).sub.2).sub.4-b
(b) a silicon-nitrogen compound having the formula ##STR1## and
(C) A SILICON-NITROGEN POLYMER COMPRISING
(1) FROM 3 TO 100 MOLE PERCENT OF UNITS SELECTED FROM THE CLASS CONSISTING OF ##STR2##
(2) from 0 to 97 mole percent units represented by the formula EQU (R*).sub.c SiO.sub.(4-c/2)
wherein R* is a monovalent hydrocarbon radical or halogenated monovalent hydrocarbon radical as further defined in the patent.
U.S. Pat. No. 3,024,126 of Brown teaches a method of solvent treatment of reinforcing silicas with hydroxyl or alkoxy silanes and siloxanes in contact with certain amine, quaternary ammonium, and organometallic compounds.. The amine is further defined as ammonia or any amino compound with a basic dissociation constant in dilute solution in water of at least 10.sup.-7 at 25.degree. C., thus the amino compound can be ammonia, a primary amine, a secondary amine, a tertiary amine, or any combination.
In U.S. Pat. No. 3,927,057 Takamizawa et al. describe an efficient method of making organosilylamines. The organosilylamines are obtained from reacting triorganohalosilanes of the general formula R.sub.3 *SiX with a nitrogen-containing compound selected from the group consisting of ammonia and amines represented by the general formula R.sub.2 *NH, wherein R* is further defined in the patent.
It has been found that specific combinations of diorganopolysiloxane, reinforcing silica, and process aids or treating agents may impart particular properties to the cured elastomers. In U.S. Pat. No. 4,008,198 Krohberger et al. have taught that a highly viscous diorganopolysiloxane mixed with a reinforcing silicon dioxide filler, a hexaorganodisilazane, and a nitrogen containing compound having at least one triorganosilyl group in which at least one nitrogen atom is linked either directly to a silicon atom or via an oxygen atom, but no more than one triorganosilyl group is linked directly to a nitrogen atom and no more than one condensable group is linked to a silicon atom yields a composition which may be cured by the addition of a curing agent to form highly transparent or optically clear elastomers. Included as an example of many such nitrogen containing compounds taught are aminorganosiloxanes such as those corresponding to the general formula R.sub.3 *Si(OSiR.sub.2 *)pNR.sub.2 * where R* is as further defined in the patent and p is a whole number having a value of from 1 to 20. In U.S. Pat. No. 3,122,516 Polmanteer taught that a great improvement in the high temperature strength of silicon rubber can be obtained by incorporating certain modified silica fillers into otherwise conventional silicone rubber formulations. These fillers were made up of SiO.sub.2 units or combinations of SiO.sub.2 units and R*SiO.sub.1.5 units and had their surface saturated with R.sub.n *SiO.sub.(4-n/2) units (I) and R.sub.x *(CH.sub.2 .dbd.CH)SiO.sub.(3-x/2) units (II) such that (I) units were present in amounts of 4 to 29.9 per 100 filler units and (II) units were present in amounts of 0.1 to 2 per 100 filler units wherein the total of (I) and (II) units was from 6 to 30 units per 100 filler units. R* is a monovalent hydrocarbon radical or halogenated monovalent hydrocarbon radical as further defined in the patent.